9000 Hours Operation of a 25 Solid Oxide Cells Stack in Steam Electrolysis Mode

The operation of 25 solid oxide cells stacks in steam electrolysis mode over 9000 hours is reported. The stack has been operated at current densities of 0.57 and 0.72 A/cm2, using a 50% steam conversion, in the 750-780°C temperature range. Performance degradation rates of 2.30%/ kh are reported, with some non-homogeneity in the stack repeat units behavior observed. Stack repeat units located at the bottom of the stack feature degradation rates below 2%/kh. The possibility to use the operating temperature as a buffer to counter the performance degradation is highlighted. The stack performance was not affected by incidents that occurred during the test.